The flag of the United States has 13 stripes because the stripes correspond to the first 13 colonies that declared independence from England. The stars on the flag match the current number of states in the union.
Since the 1770s, the U.S. flag has gone through multiple changes. One of the first versions featured the thirteen stars with a British Union Jack in the upper corner. In 1777, the Second Continental Congress passed a resolution that the flag should have thirteen stripes and thirteen white stars in a blue background. In 1795, the number of stripes and stars increased from 13 to 15. In 1818, President James Munroe signed a Congressional act that reduced the 15 stripes back to 13 to commemorate the original colonies. This act also raised the number of stars to 20 and stipulated that a star would be added with the admission of each new state to the union.
In 1912, President William Howard Taft signed an executive order standardizing the placement of the stars on the flag, and in 1959, President Dwight Eisenhower signed an executive order changing the arrangement of the stars to reflect the addition of new states to the union. As of 2014, the United States flag has 50 stars in alternating rows of five and six.